He offers guided walking tours to search for the special rocks, which glow when exposed to UV light due to the presence of the fluorescent mineral Sodalite.

"I've been a rock picker all my life. I got it from my dad, who got it from his dad," said the 43-year-old, who has a side business as an agate dealer.

After getting a hold of the right type of light, Rintamaki first found a Yooperlite one night last year. "I was just screaming on the beach I was so happy," Rintamaki said, although he had no idea what he was holding -- even after doing some Googling and asking around.

"I took them to all the rock and mineral shows and no one could identify them," he said, "...so I nicknamed them "Yooperlites."

It may seem like a funny name; but as Rintamaki points out, Michigan's beloved Petoskey stone is in fact hexagonal coral, though hardly anyone calls it that.

While he wasn't the first person to discover the mineral itself, Rintamaki is credited with bringing it to Michigan Tech University geologists who were able to verify for the first time that there is Sodalite in Michigan; perhaps brought down from Canada by glaciers.